O-Hydroxyalkylation of 1,1-dihydroperfluorinated alcohols has most commonly been conducted using alkylene oxide reagents. U.S. Pat. No. 3,394,115, for example, teaches the O-hydroxyethylation of 2,2,2-trifluoroethanol using ethylene oxide. Despite employing a 1:1 stoichiometry of reactants, the monohydroxyethylated product was obtained in only 50 percent yield, with the simultaneous formation of the product resulting from addition of two molecules of ethylene oxide in 25 percent yield. The problem of polyalkylation was circumvented somewhat in U.S. Pat. No. 3,532,674 (Example 1, Method B). By slowly adding, over the course of several hours, two-thirds of an equivalent of ethylene oxide per equivalent of 1,1-dihydroperfluorinated alcohol, a reasonably good selectivity to the monohydroxyethylated product was achieved. The conversion (based on starting alcohol), however, was not indicated and, even so, the theoretical yield could only be 67 percent. The problem with alkylene oxides, aside from their toxicity and well-known explosion potential, is that they do not discriminate well between starting and product alcohols.
In contrast, alkylene carbonates have been utilized to provide O-hydroxyalkylated phenols (cf. T. Yoshino, et al., Bull. Chem. Soc. Japan, 46, 553 (1973)) and perfluoroalkanesulfonamides (cf. H. Niederpruem, et al., Liebigs Ann. Chem, 11 (1973)). Alkylene carbonates are stable, relatively inexpensive, non-toxic, and non-gaseous (at room temperature and pressure) compounds.
In related work, ethylene sulfite has been utilized to provide O-hydroxyethylated 1,1-dihydroperfluorinated alcohols (see U.S.S.R. 482,433 (1976)). Aside from the increased cost of the reagent, emission of the extremely acidic sulfur dioxide by-product can lead to significant processing and pollution problems.
A process for the O-hydroxyalkylation of 1,1-dihydroperfluorinated alcohols has been disclosed in U.S. Pat. No. 4,906,792. This process is particularly useful with alcohols with boiling points of at least 140.degree. C.